Auditory evoked potentials in Down's syndrome

Short-, middle- and long-latency auditory evoked potentials (SAEPs, MAEPs and LAEPs) were examined in 12 subjects with Down's syndrome and in 12 age-matched normal subjects. In comparison with the normal subjects, Down subjects showed shorter latencies for SAEP peaks II, III, IV and V (and correspondingly shorter interpeak intervals I–II and I–III) so long as stimulus intensity was at least 45 dB SL. The MAEP peak Na had a longer latency in Down subjects than in normal subjects, but not the Pa latency. In passive oddball experiments for LAEPs, the latencies of all components from N1 to P3 were progressively longer in Down subjects, and the N2-P3 amplitude increased slightly between the first and fourth blocks of stimuli (whereas in the normal subjects it decreased). These alterations in auditory evoked potentials, which may correlate with cerebral alterations in organization and responsiveness responsible for deficient information processing, may constitute an electrophysiological pattern that is characteristic of Down's syndrome.     

Auditory evoked potentials in the Japanese monkey.

Auditory sensitivity based on auditory brain stem response (ABR), whole nerve action potential (AP), and cochlear microphonics (CM) to tone bursts of 0.5-8 kHz were compared with behavioral audiometry in the Japanese monkeys. Although sensitivity loss at 4-6 kHz was observed in these potentials, an increase in sensitivity at 8 kHz was obtained only in the ABR. Thus the sensitivity loss at 4-6 kHz originates at the peripheral system and the increased sensitivity at 8 kHz originates at the central.     

Auditory evoked potentials to indifferent and meaningful stimuli in young children

Auditory evoked potentials (AEP) of the frontal, central and parietal cortical areas of the left hemisphere in response to an indifferent sound stimulus and to a stimulus with same physical characteristics, but with acquired informational significance, were studied in healthy children of the 3-d year of life. In the last case the amplitude of the AEPs in all recorded areas rose and the latencies of late components in the parietal area became longer. Moreover, the components of AEP got more complex owing to a greater manifestation of the late positive component P3 in all recorded areas and particularly in the parietal one.     

Determination of conduction times of the peripheral and central parts of the sensory pathway using evoked somatosensory potentials

Determination of conduction times of the peripheral and central parts of the sensory pathway using evoked somatosensory potentials. Acta physiol. pol., 1985, 36 (3): 216-223. Simultaneous recording of the somatosensory evoked potentials (SEP) from Erb's point, neck and scalp allows investigation of the peripheral and central conduction times. The early components of the SEP produced by stimulation of the median nerve at the wrist were recorded using standardized electrode locations in 15 normal subjects. The difference of the latencies between the first peak of the cortical response (N20) and the peak of the neck response (N14) reflects, probably, the conduction time between the dorsal column nuclei and the cortex. Its value was 6 +/- 0.7 msec. The conduction time difference (between peak Erb's point response (N9) and N14) was 5.5 +/- 0.5 msec and it reflected the peripheral conduction time. For diagnostic application the lower limit of the response amplitudes was determined also for every component.     

Laminar analysis of hippocampal potentials evoked by peripheral stimulation

From areas SA₁ and SA₂ of the dorsal hippocampus of unanesthetized rabbits immobilized with d-tubocurarine a laminar analysis was made of evoked potentials (EP) in response to stimulation of the sciatic nerves. Inversion of the initial surface-positive phase of the EP was observed at the level of the pyramidal layer. The subsequent surface-negative phase reached a maximum value in the layer of basal dendrites of the pyramidal cells. The initial portion was inverted somewhat above the pyramidal layer and reached its maximum value approximately at the boundary of the pyramidal and radial layers. The change in sign of the remaining portion of this component occurred 0.3–0.4 mm deeper than the pyramidal layer. It is suggested that both components of the EP picked up from the hippocampal surface are due to an excitatory postsynaptic potential (EPSP) at the apical (positive phase), and basal (negative phase) dendrites. The positivity in the region of the pyramidal somata appears to be an extracellular reflection of a composite postsynaptic potential (IPSP) generated in this region.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 4. pp. 434–438, July–August, 1970.     

Important relation between EEG and brain evoked potentials

In this study, we analyze the important relation between the spontaneous and evoked activities of the substructures of the cat brain, such as the reticular formation, hippocampus, inferior colliculus, medial geniculate nucleus and acoustical cortex, with an ensemble of systems theory methods consisting of the following steps: (1) single auditory and/or visual evoked potentials (EPs) and the spontaneous activities (EEG) just preceding the stimuli are recorded from the brain center under study; (2) selectively averaged evoked potentials (SAEPs) are obtained from the recorded EPs; (3) amplitude frequency characteristics are computed from the AAEPs by means of Fourier transform; (4) the single EEG-EP sweeps are theoretically pass-band filtered with adequate band limits determined according to the selectivities revealed by the amplitude characteristics; (5) the EEG and EP components obtained in this way are compared with regard to the amplification in the population response upon the application of the stimulus. The results of this analysis support quantitatively our prediction of various types of resonance phenomena in a number of nuclei in the cat brain and in a large scale of frequencies from 1 Hz to 1000 Hz and show that the amplification factor related to resonance phenomena has probabilistic nature. Therefore, the analogy which we have recently drawn between the behaviors of a neural population and a random-phase probabilistic harmonic oscillator is extended by assigning also the amplitude and the frequency of the oscillations as random variables. A working hypothesis for the dynamics of neuronal populations is elaborated accordingly.Presented in Part at the Third European Meeting on Cybernetics and Systems Research 1976 in Vienna, April 20–23, 1976Supported by Grant No. TAG-345 of the Scientific and Technical Research Council of Turkey     

Auditory evoked potentials in the West Indian manatee (Sirenia:Trichechus manatus)

Summary Potentials evoked by clicks and tone pips were recorded by fine wires inserted extracranially in four West Indian manatees (Trichechus manatus) in air. Sounds were delivered via padded ear phones.Averaging a few thousand trials at 20/s reveals early peaks at N5.4 (vertex negativity to a frontal reference, at 5.4 ms), P7.6, N8.8, P9.5 — probably equivalent to waves IV and VII of the typical mammalian auditory brainstem response (ABR). Averaging 100 trials at <4/s suffices to reveal a complex sequence of later peaks including N25, P80, N150 and P190; consistent smaller peaks are visible when several hundred trials are averaged.Using tone pips with a rise and fall time of 2–5 ms the carrier frequency becomes important. Evoked potential wave forms are not the same at different frequencies, bringing out the fact that frequency is not a scalar that can be compensated for by intensity. Therefore the method was not used to obtain audiograms; however the largest EPs occur in the range of 1–1.5 kHz. EPs are found up to 35 kHz; almost no evoked potential is discernible at 40 kHz but the undistorted intensity available was limited. This is in reasonable agreement with the theoretical expectation for the upper limit of behavioral hearing from Heffner and Masterton based on head size and aquatic medium.Among several ear phone placements, that over the external auditory meatus was the most effective, but only slightly so. The external canal is presumably fluid or tissue filled and sound enters over a large area.Comparing data for two species on the most effective range of frequencies and the power spectra of their vocalizations,T. manatus is lower thanT. inunguis in both respects.The results show the utility and limitations of the method of recording extracranial evoked potentials to sounds, especially for large and valuable animals under makeshift conditions.Abbreviations ABR auditory brainstem response - AEP averaged evoked potentials - EMG electromyogram - F frontal sinuses - V vertex     

Somatosensory evoked potentials in lesions of central structures of the skin-motor analyzer

To assess the role of different mechanisms in increasing the amplitude of the early components of cortical somatosensory evoked potentials (SSEPs) in lesions of central structures of the skin-motor analyzer in humans, SSEPs of the hand cortical projection zones (the points C′₃ and C′₄) and the spinal dorsal column nuclei (DCN) were recorded in parallel in response to trancutaneous electrostimulation of the median nerve in the carpal region in two groups of subjects. The control group included 26 healthy volunteers aged 39–62 years; the other group included 12 patients aged 45–63 years with hemiplegia and sensory disorders due to a stroke experienced 8–24 months before the electrophysiological studies. A significant (from P < 0.05 to P < 0.01) increase in the amplitude of the early SSEP components of the intact hemisphere and several early SSEP components of the affected hemisphere (with a decrease in the amplitude of the other components) and no changes in DCN SSEPs were observed in the patients compared to the control group, which was interpreted as a manifestation of local mechanisms causing an isolated increase in cortical excitability without changes in the reactivity of DCN.     

Study by auditory evoked potentials of the efficacy of transcutaneous electric stimulation in the treatment of tinnitus

Thirty patients complaining about tinnitus were treated by transcutaneous tragal electrical stimulation. The effect of this treatment has been evaluated by BASR recordings before and after treatment. Taking into account the subjective results three groups are described. The first one (10 patients) is relieved of tinnitus. In second and third group the symptoms still exist, whatever the electrode's position (anode or cathode in tragal position). When BASR are studied before the electrical stimulation no inter-subjects difference can be found. After stimulation, the left delta I-V latency is significatively lengthened, and the wave I latency is shortened in the first group. The study of the two other groups do not reveal any difference between the pre- and the post- stimulation evaluation. So the BASR appears to be a good predictive tool for tinnitus suppression by electrical stimulation.     

Auditory evoked potentials from the primary auditory cortex of the cat: topographic and pharmacological studies

Wave VI (8.4 msec) of the brain-stem auditory evoked potential (BAEP) was maximal in a discrete region of primary auditory cortex (AI) of the anesthetized cat. Wave VI underwent rapid amplitude decreas over millimeter distances in the AI region and followed high stimulation rates. Wave VI did not show intracortical polarity inversion nor was it abolished by epicortical or intracortical GABA administration. The data are compatible with a wave VI source in the terminal axons of the thalamo-cortical radiations.Middle latency auditory responses (MAEPs) generated 10–40 msec after auditory stimulation were also recorded in a circumscribed area of AI. In contrast to wave VI, these primary auditory cortex potentials (Pa 18.3 msec; Nb 31.9 msec) underwent transcortical polarity inversion, correlated with intracortical multi-unit activity in the AI region and were reversibly altered or abolished by epicortical or intracortical GABA adminstration to the AI region. The data suggest that the Pa and Nb components of the cat MAEP are intracortically generated by neuronal elements in the AI region.     

Auditory evoked potential audiometry in fish

A recent survey lists more than 100 papers utilizing the auditory evoked potential (AEP) recording technique for studying hearing in fishes. More than 95 % of these AEP-studies were published after Kenyon et al. introduced a non-invasive electrophysiological approach in 1998 allowing rapid evaluation of hearing and repeated testing of animals. First, our review compares AEP hearing thresholds to behaviorally gained thresholds. Second, baseline hearing abilities are described and compared in 111 fish species out of 51 families. Following this, studies investigating the functional significance of various accessory hearing structures (Weberian ossicles, swim bladder, otic bladders) by eliminating these morphological structures in various ways are dealt with. Furthermore, studies on the ontogenetic development of hearing are summarized. The AEP-technique was frequently used to study the effects of high sound/noise levels on hearing in particular by measuring the temporary threshold shifts after exposure to various noise types (white noise, pure tones and anthropogenic noises). In addition, the hearing thresholds were determined in the presence of noise (white, ambient, ship noise) in several studies, a phenomenon termed masking. Various ecological (e.g., temperature, cave dwelling), genetic (e.g., albinism), methodical (e.g., ototoxic drugs, threshold criteria, speaker choice) and behavioral (e.g., dominance, reproductive status) factors potentially influencing hearing were investigated. Finally, the technique was successfully utilized to study acoustic communication by comparing hearing curves with sound spectra either under quiet conditions or in the presence of noise, by analyzing the temporal resolution ability of the auditory system and the detection of temporal, spectral and amplitude characteristics of conspecific vocalizations.